/*
 * Copyright (c) 2006 Israfil Consulting Services Corporation
 * Copyright (c) 2006 Christian Edward Gruber
 * All Rights Reserved
 * 
 * This software is licensed under the Berkeley Standard Distribution license,
 * (BSD license), as defined below:
 * 
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this 
 *    list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice, 
 *    this list of conditions and the following disclaimer in the documentation 
 *    and/or other materials provided with the distribution.
 * 3. Neither the name of Israfil Consulting Services nor the names of its contributors 
 *    may be used to endorse or promote products derived from this software without 
 *    specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
 * IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, 
 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY 
 * OF SUCH DAMAGE.
 * 
 * $Id: GenericCache.java 129 2006-12-31 23:20:02Z cgruber $
 */
package net.israfil.foundation.caching;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


/**
 * A non-thread-safe cache object
 * 
 * @author <a href="mailto:cgruber@israfil.net">Christian Edward Gruber</a>
 */
public class GenericFetcherCache implements FetcherCache {
	
	private Map<String,Object> _caches = new HashMap<String,Object>();
		
	/**
	 * Retrieves an object from a path in the cache
	 * @param cacheName A string identifying from which cache the object will be retrieved
	 * @param An array of path items identifying the path through the map keys.
	 */
	public Object get(Fetcher fetcher, String cacheName, String itemKey, String ... path) {
					
		// Fetch the map containing the item.
		Map<String,Object> cache = _getLocationInMap(_caches,new ArrayList<String>(_prepPathList(cacheName,path)));

		// Get the item from the map
		Object o = cache.get((itemKey==null) ? "__NULL__" : itemKey);
		if (o == null) {
			// Item doesn't exist, so try to fetch, then retrieve again.
			fetcher.fetch();
			o = cache.get((itemKey==null) ? "__NULL__" : itemKey);
		}
		return o;		
	}
	

	/**
	 * A method to set values within the cache, to be used by Fetcher implementations
	 * in setting up the cache when they fetch.
	 */
	public void set(String cacheName, String itemKey, Object value, String ... path) {
		List<String> pathList = _prepPathList(cacheName,path);
		Map<String,Object> cache = _getLocationInMap(_caches,new ArrayList<String>(pathList));
		cache.put(itemKey,value);
	}

	/**
	 * Creates a List that contains the pathelements, starting from the 
	 * cache name down to the bottom, but excluding the actual final path
	 * item.
	 */
	static List<String> _prepPathList(String cacheName,String[] pathElements) {
		List<String> pathList;
		if (pathElements == null || pathElements.length < 1) {
			pathList = new ArrayList<String>();
		} else {
			// Need to make this explicitly an arrayList, so that
			// add(index,value) will work.
			pathList = new ArrayList<String>(Arrays.asList(pathElements));
		}
		pathList.add(0,cacheName);	
		return pathList;
	}
	
	/**
	 * Recursively traverses the cache map, creating maps at path locations
	 * where they do not already exist.
	 */
	@SuppressWarnings("unchecked")
    static Map<String, Object> _getLocationInMap(
            Map<String, Object> currentMap, List<String> cachePath) {
		if (cachePath == null || cachePath.size() < 1) return currentMap;
		String cacheName = (String)cachePath.remove(0); // pull the first one
		
		Object cacheObject = (Map<String,Object>)currentMap.get(cacheName);
		if (cacheObject == null) {
			cacheObject = new HashMap<String,Object>();
			currentMap.put(cacheName,cacheObject);
		}
		if (! (cacheObject instanceof Map))
			throw new IllegalArgumentException("Attempted to find a map at location ("+cachePath+") in cache ("+cacheName+"), but found a " + cacheObject.getClass().getName() + ".");
		Map<String,Object> cache = (Map<String,Object>)cacheObject;
		
		return _getLocationInMap(cache,cachePath);
	}

	
}
